Apollo is one of the most important and complex of the Olympian deities in classical Greek and Roman religion and Greek and Roman mythology. The ideal of the kouros (a beardless, athletic youth), Apollo has been variously recognized as a god of music, truth and prophecy, healing, the sun and light, plague, poetry, and more. Apollo is the son of Zeus and Leto, and has a twin sister, the chaste huntress Artemis. Apollo is known in Greek-influenced Etruscan mythology as Apulu.Though the proportions were always important in Greek art, the appeal of the Greek sculptures eludes any explanation by proportion alone. The statues of Apollo were thought to incarnate his living presence, and these representations of illusive imaginative reality had deep roots in the Minoan period, and in the beliefs of the first Greek speaking people who entered the region during the bronze-age. Just as the Greeks saw the mountains, forests, sea and rivers as inhabited by concrete beings, so nature in all of its manifestations possesses clear form, and the form of a work of art. Spiritual life is incorporated in matter, when it is given artistic form. Just as in the arts the Greeks sought some reality behind appearances, so in mathematics they sought permanent principles which could be applied wherever the conditions were the same. Artists and sculptors tried to find this ideal order in relation with mathematics, but they believed that this ideal order revealed itself not so much to the dispassionate intellect, as to the whole sentient self. Things as we see them, and as they really are, are one, that each stresses the nature of the other in a single unity.